MCP Protocol Integration
Claude Code acts as an MCP (Model Context Protocol) client, connecting to external MCP servers to extend its tool and resource capabilities.
Connection Management
src/services/mcp/client.ts supports multiple transports: stdio, SSE (with OAuth), HTTP, WebSocket, SDK (in-process), Claude.ai proxy, and IDE-specific transports. Connections are lazy (memoized).
Connection Flow
connectToServer(config) -> pick transport -> create Client -> connect
// Returns: connected | failed | needs-auth
useManageMCPConnections (React hook) manages reconnection, listens for ToolListChangedNotification, and refreshes tools.
Tool Discovery & Integration
Each discovered tool gets a local Tool object cloned from MCPTool template with name mcp__serverName__toolName, overriding description, schema, call function, and permissions.
MCP Configuration
Configs merge from multiple sources: enterprise policy (exclusive override) -> user (~/.claude/.mcp.json) -> project (.claude/.mcp.json) -> plugins. Supports ${VAR} environment variable expansion.
MCP Resources & Skills
ListMcpResourcesTool and ReadMcpResourceTool handle MCP resources. When MCP_SKILLS feature flag is on, MCP prompts can be loaded as skills.
Key Source Files
| File | Responsibility |
|---|---|
src/services/mcp/client.ts | MCP client: connect, discover, call |
src/services/mcp/config.ts | MCP config merging |
src/services/mcp/types.ts | Type definitions |
src/tools/MCPTool/MCPTool.ts | MCP tool template |
Next
Go to 10-multi-agent.md to learn about multi-agent coordination.
Hands-on Experiment
This chapter has a corresponding Python experiment:
Covers: MCP protocol, tool discovery, tool pool merging